Ghost Recon Advanced Warfighter or Prey?

I'm going to Gamestop tomorrow to pick up a cheap game from their used booth. I'm curious, should I buy Prey or GRAW? Prey is 9.99 while GRAW is 14.99 so the price isn't a concern. It's mainly how long each game will last in their single player content, since I don't get to play online very much until I go to my mother's house.

So, which game do you recommend?

i would go with graw. I've played prey, and it was a fun game until about midway through, then things became pretty repetitive. I would go with GRAW personally because i like the realism, and when you do get the opportunity to play multiplayer i think it's one of the best experiences on live. I would say it's worth every bit of 14.99 for what you get.